Supramolecular Complexes of C₈₀-Based Metallofullerenes with [12]Cycloparaphenylene Nanoring and Altered Property in a Confined Space

Metallofullerenes have a cage-shaped molecular structure and special properties derived from encapsulated metal atoms. Owing to the ball-like fullerene cage, it is still a challenge to manipulate the metallofullerene molecule and to control its properties. Herein, we use the molecular carbon nanoring of [12]cycloparaphenylene to hoop the C₈₀-based metallofullerene Y₃N@C₈₀ and azafullerene Y₂@C₇₉N, resulting in a stable supramolecular complex, induced molecule orientation, changed assembly behavior, and tunable spin state. These supramolecular complexes and their host-guest interactions were systematically characterized by DFT-calculations, spectroscopy, NMR, and electrochemical analysis. Scanning tunneling microscopy was employed to reveal that the metallofullerene guests dominate the assembly process on the Au(111) surface and the [12]CPP nanoring can change the weak van der Waals forces and influence self-assembly. Moreover, the electron spin in paramagnetic Y₂@C₇₉N was employed to percept the host-guest interaction, and it showed anisotropic spin-metal couplings due to its insufficient rotational averaging in a confined space of the nanoring. The special spin character of Y₂@C₇₉N⊂[12]CPP was also investigated in its solid state, and it exhibits the independent spin of Y₂@C₇₉N separated by a nanoring. This study provides a strategy to hoop the ball-like C₈₀-based metallofullerenes and modulate their electronic and magnetic properties using a circular nanoring. Metal-induced orientation, self-assembly characters, and susceptible electron spin for these supramolecular complexes reveal a great significance in molecule science and nanotechnology.